This invention relates to Colt M16 automatic carbines and specifically to a retro-fit gas system for controlling the firing rate.
The Colt M16 rifle has a gas operated system having a gas port located at a predetermined point on the barrel near its forward end. The port detects the accummulation of gases when a bullet has been fired. This gas pressure is fed back through a gas line to a bolt carrier mechanism which unlocks the bolt, ejects the cartridge, feeds in a new cartridge, and locks the bolt in the conventional manner that all M16's or other repeating rifles use.
The standard Colt M16 rifle has a 20 inch barrel and fires approximately 650 rounds of ammunition per minute. The shorter carbine has 10 inch to 16 inch barrels and a shorter gas tube and they fire at a much higher rate of fire. At this rate of fire, everything becomes critical and the ammunition must be up to spec, the barrel must be clean, and other conditions must be proper, or the Colt carbine jams up. When the barrel is shortened to 10, 12, or 14 inches long, the timing relationship between the pressure and the bolt carrier mechanism causes the bolt mechanism to be operated sooner and at a time when all of the pressure in the barrel has not been reduced to zero. This causes the chamber to be opened under pressure which has a tendency to hold the cartridge in place since the cartridge expands under intense pressure and some small amount of time is necessary for the cartridge to contract as the pressure reduces to 0 before the cartridge can be expelled.
Opening the breech under pressure is dangerous at best since the casing is being expelled while still in an expanded state and a tendency for jamming is very high.
These problems have been addressed in what is termed in the field as a brute force method by utilizing special lubricants to ease the ejection of the casing. These new lubricants do improve the situation, however, the problem is not completely solved because while the instance of jamming has been reduced, when a barrel has been shortened from its standard 16 inches in length to a shorter length, this reduces the timing cycle and the rate of fire in the carbine is increased to between 1300 to 1600 rounds a minute. With this increased rate of fire it is even more important that the chamber be shiny and polished and that the ammunition be up to spec. Even in the absence of the tendency to jam the rate of fire is so fast that the gun becomes almost unuseable and unwieldy. Additionally, the excess rate of fire is very wasteful of ammunition, and inaccurate at best and over a short period of time heat generated by this high rate of fire causes additional damage to the gun, again increasing the tendency to jam and at an excessive rate.
It is an object of the invention to provide a novel retro-fit gas system for controlling the firing rate of the Colt M16 automatic carbine that requires no modifications to the existing structure.
It is another object of the invention to provide a novel retro-fit gas system for controlling the firing rate of the Colt M16 automatic carbines having barrels shorter that 16 inches that will allow them to operate in the approximate range of 800 rounds per minute.
It is also an object of the invention to provide a novel retro-fit gas system for controlling the firing rate of the Colt M16 automatic carbines that is economical to manufacture and market.
It is an additional object of the invention to provide a novel retro-fit gas system for controlling the firing rate of the Colt M16 automatic carbine that is easily and quickly installed in the rifle.